With the progress of process technology, a thin film transistor has been widely used in a display to meet the need for a thinned and miniaturized display. During the operation of the display, the thin film transistor is easily irradiated by light, and when the light is irradiated to the active layer, the OFF state leakage current thereof will be increased, leading to the deterioration of characteristics of the thin film transistor.
There is a conventional thin film transistor comprising a gate, a gate insulating layer formed on the gate, an active layer formed on the gate insulating layer, and a source and a drain formed on the active layer and spaced from each other. In this structure, the gate is located below the active layer, the light irradiated from below the active layer can be blocked, while the light irradiated from above the active layer is not blocked and can be irradiated from between the source and the drain to the active layer, thereby causing the deterioration of the characteristics of the thin film transistor.